No mark , you dont have to worry about them being similar. Unless its an exact duplicate , or it's named the same as the ship , for instance , ship fireballs or whatever (i dont like startrek) , so using them as inspiration wont get u in trouble , at least thats what i think. I mean , look at the other sci fi stuff , a lot of it is similar , you cant get someone in trouble like that , usually it would have to be exactly the same or be named the same , names tend to get u in trouble more.